Semiconductor dies are fabricated on a semiconductor substrate by various manufacturing operations such as deposition, photolithography, etching, implantation or the like. In recent years, silicon-on-insulator (SOI) substrate has been developed as as an alternative substrate. The SOI substrate is a substrate which has a device silicon layer separated from an underlying handle silicon wafer by an insulative layer. The SOI substrate has advantages such as reduced parasitic capacitances, reduced power consumption, reduced current leakage and increased ability to operate at more elevated temperature.
The handle silicon wafer has high resistivity, which allows to meet some application requirements such as device-to-device isolation, passive device Q-factors, etc. Due to the low dopant of the handle silicon wafer, carriers tend to accumulate adjacent to the interface between the handle silicon wafer and the insulative layer. The voltage applied to the overlying device may interact with the accumulated carriers, deteriorating performance of the overlying device. In some application such as RF application, the RF signals may suffer from cross-talk and non-linear distortion.